When Elisabeth, Jim, Malcolm and Taylor investigate radio silence at a nearby scientific outpost, they discover an outbreak of a mysterious virus causing memory loss, paranoia and eventually death. The group must work together to find a cure before they lose their sanity and all of Terra Nova is infected.

When an orphaned "Sixer" girl comes to Terra Nova seeking asylum, Jim and Shannon are at odds if they can trust her; Mira plots to reclaim a valued possession; Taylor begins to suspect there is a traitor in his midst and Reynolds admits his feelings for Maddy.

The colony falls victim to its first murder, and Jim and Taylor must find the perpetrator. Also, Skye helps Josh find a way to get Kira, his girlfriend from 2149, to the past, while Elisabeth and Zoe race to help an unborn Ankylosaurus survive.